Thiosemicarbazone derivatives, thiazolyl hydrazones, effectively inhibit leukemic tumor cell growth: Down-regulation of ribonucleotide reductase activity and synergism with arabinofuranosylcytosine.

Cellular growth inhibition exerted by thiosemicarbazones is mainly attributed to down-regulation of ribonucleotide reductase (RNR) activity, with RNR being responsible for the rate-limiting step of de novo DNA synthesis. In this study, we investigated the antineoplastic effects of three newly synthesized thiosemicarbazone derivatives, thiazolyl hydrazones, in human HL-60 promyelocytic leukemia cells. The cytotoxicity of compounds alone and in combination with arabinofuranosylcytosine (AraC) was determined by growth inhibition assays.